1.9.1 and Knockout.js ViewModel binding appears broken

I believe the 1.9.1 update has broken interoping with Knockout.js viewmodels

I have set up 1 jsfiddles 1 for 1.9.0 and 1 for 1.9.1;

1.9.0 seems to work fine with Knockout.js I have a jsfiddle here. http://jsfiddle.net/bdetchison/b4SsE/.
1.9.1 seems to not update when Knockout.js's ViewModel has changed. Here is a jsfiddle. http://jsfiddle.net/bdetchison/27DZR/


**Edit
moved to bug reports